Ji et al. Journal of Cardiothoracic Surgery (2015) 10:16 DOI 10.1186/s13019-015-0216-y

RESEARCH ARTICLE Open Access

Impact of smoking on early clinical outcomesin patients undergoing coronary artery bypassgrafting surgeryQiang Ji1, Hang Zhao2, YunQing Mei1*, YunQing Shi3, RunHua Ma3 and WenJun Ding3*

Abstract

Background: To evaluate the impact of persistent smoking versus smoking cessation over one month prior tosurgery on early clinical outcomes in Chinese patients undergoing isolated coronary artery bypass grafting (CABG)surgery in a retrospective study.

Methods: The peri-operative data of consecutive well-documented patients undergoing isolated CABG surgeryfrom January 2007 to December 2013 were investigated and retrospectively analyzed. All included patients weredivided into either a non-smoking group or a smoking group according to preoperative smoking records. Furthermore,smokers were divided into either a former smoking subgroup (smokers with smoking cessation over 1 month beforesurgery) or a current smoking subgroup (persistent smokers).

Results: A total of 3730 consecutive patients (3207 male patients and mean 63.6 ± 9.5 years) undergoing isolated CABGsurgery were analyzed. Persistent smokers had significantly higher incidence of postoperative pulmonary complicationsas compared to non-smokers (7.8% vs. 4.5%, p = 0.0002). No significantly differences in both surgical mortality and majorpostoperative morbidities between smokers with smoking cessation over 1 month before surgery and non-smokers werefound. In multiple logistic regression analysis, the risk of postoperative pulmonary complications in persistent smokers was2.41 times than that in non-smokers, whereas the risk of postoperative pulmonary complications in smokers with smokingcessation over 1 month before surgery was similar to non-smokers.

Conclusions: Persistent smokers had a higher incidence of pulmonary complications following CABG as compared tonon-smokers. Smoking cessation more than 1 month before surgery was expected to reduce early major morbiditiesfollowing CABG surgery.

Keywords: Persistent smoking, Smoking cessation, Early clinical outcomes, Coronary artery bypass grafting surgery

BackgroundSmoking is a major risk factor for coronary heart dis-ease. Previous study [1] reported smoking cessation hasbrought about a reduction of incidence of coronary heartdisease of 12%. Coronary artery bypass grafting surgery(CABG) is an important means of treatment of coronaryheart disease. Warner MA and colleagues [2] conducteda blinded prospective study and showed that smokerswith smoking cessation less than 2 months before CABG

* Correspondence: jiqiang1977@aliyun.com; dwj12191@163.com1Department of Thoracic Cardiovascular Surgery of Tongji Hospital of TongjiUniversity, 389 Xincun Rd, Shanghai 200065, P.R. China3Department of Cardiovascular Surgery of Zhongshan Hospital of FudanUniversity, 180 Fenglin Rd, Shanghai 200032, P.R. ChinaFull list of author information is available at the end of the article

© 2015 Ji et al.; licensee BioMed Central. ThisAttribution License (http://creativecommons.oreproduction in any medium, provided the orDedication waiver (http://creativecommons.orunless otherwise stated.

surgery had a higher incidence of postoperative pulmon-ary complications as compared to smokers with smokingcessation more than 2 months before CABG surgery.With the progress in surgical techniques and postopera-tive care, major morbidities following CABG were alsoon the decline. Recently, it is reported that smokingcessation more than 1 month before CABG procedureevidently reduced pulmonary complications followingCABG surgery [3].So far, China becomes the largest tobacco producer

and consumer in the world, with more than 300 millionsmokers [4]. However, there are few reports about theimpact of smoking on clinical outcomes of Chinese patientsundergoing isolated CABG surgery. In this retrospective

is an Open Access article distributed under the terms of the Creative Commonsrg/licenses/by/4.0), which permits unrestricted use, distribution, andiginal work is properly credited. The Creative Commons Public Domaing/publicdomain/zero/1.0/) applies to the data made available in this article,

Ji et al. Journal of Cardiothoracic Surgery (2015) 10:16 Page 2 of 7

study, we aimed to evaluate the impact of persistent smok-ing vs. smoking cessation over 1 month before surgery onearly postoperative clinical outcomes through reviewing3730 consecutive Chinese patients undergoing isolatedCABG procedure.

MethodsSubjectsAfter approval by the ethics committee of Tongji hospitalaffiliated to Tongji University, in accordance with theDeclaration of Helsinki, we reviewed the records of con-secutive well-documented patients undergoing either emer-gency or scheduled isolated CABG procedure with orwithout cardiopulmonary bypass from January 2007 toDecember 2013. Any patient with incomplete informationfrom preoperative smoking records was excluded from thisstudy. According to smoking records before CABG surgery,all included patients were divided into either a smokinggroup (smokers) or a non-smoking group (non-smokers).Furthermore, the smoking group (smokers) was dividedinto either a former smoking subgroup (smokers withsmoking cessation over 1 month before CABG surgery) ora current smoking subgroup (persistent smokers). Data col-lection was performed by trained staff (two people), andthey did not know the purpose of this study.The details of the coronary artery lesions (SYNTAX

score [5]), in association with the preoperative characteris-tics, was carefully evaluated for assignment to CABG with(on-pump CABG) or without cardiopulmonary bypass(off-pump CABG). In every patient complete anatomicrevascularization of all diseased vessels with a luminaldiameter greater than or equal to 1 mm was considerednecessary. If the operating surgeon judged a complete re-vascularization feasible on the beating heart, off-pumpCABG was scheduled. In patients in whom the location orthe quality of the target vessels and the preoperative char-acteristics (such as left ventricular end diastolic dimension,left ventricular ejection fraction, etc.) was considered tomake off-pump revascularization technically too challen-ging, on-pump CABG was scheduled. All the procedures(either off-pump or on-pump CABG) were performed bythe same surgical team and there were no differences inthe rate of adoption of off-pump CABG between the dif-ferent surgeons. In our center, off-pump CABG had beenperformed routinely for >5 years before the launch of thetrial, and all of the operations were performed by 3 sur-geons highly experienced in both off-pump and on-pumpsurgery (each of the 3 participating surgeons performed atleast 50% of their CABG procedures as off-pump CABG).

Definition of surgical mortality and major postoperativemorbiditiesSurgical mortality was defined as death that occurredduring the same hospitalization or within 30 days of

CABG surgery [6]. Major postoperative morbidities in-cluded postoperative myocardial infarction, low cardiacoutput syndrome (LCOS), new onset atrial fibrillation,cardiac arrest or ventricular fibrillation, pulmonary com-plications, renal failure, stroke, gastro-intestinal compli-cations, incision infection, and multiple system organfailure (MSOF). Postoperative myocardial infarction wasdefined by either the appearance of new Q waves in 2 ormore contiguous leads on the electrocardiogram, or anincrease in the creatine kinase MB isoenzyme fraction ofmore than 50U, in concert with an excess of 7% of thetotal creatinine kinase level [7]. LCOS was consideredwith those who met the following criteria before dis-charge from first hospitalization in the intensive careunit immediately after CABG surgery: 1. Need for ino-tropic support with vasoactive drugs or mechanical cir-culatory support with intra-aortic balloon pump tomaintain systolic blood pressure greater than 90 mmHgafter correction of all electrolytes and blood gas abnor-malities while adjusting preload volume to its optimalvalues; 2. Signs of impairment of body perfusion aftercorrection of all electrolytes and blood gas abnormalitieswhile adjusting preload volume to its optimal values [8].New onset atrial fibrillation was considered as postoper-ative intermittent or persistent new onset atrial fibrilla-tion before discharge. Cardiac arrest or ventricularfibrillation was defined as postoperative unexplainedheart arrest or ventricular fibrillation before discharge,resulting in loss of cardiac ejection function, and requir-ing cardiopulmonary resuscitation. Pulmonary complica-tions included postoperative pneumonia which wasdefined as a positive result in a sputum culture requiringanti-infective treatment, or chest X-ray diagnosis ofpneumonia following CABG surgery [9] and postopera-tive respiratory failure which was defined as the durationof mechanical ventilation more than 48 h after surgeryor unplanned re-intubation within 30 days of surgery[10] (although some previous reports defined postopera-tive respiratory failure as requiring mechanical ventila-tion > 72 h or re-intubation following surgery, this studydefined postoperative respiratory failure as requiringmechanical ventilation > 48 h or re-intubation followingsurgery in view of the majority of included patientsundergoing off-pump CABG). Renal dysfunction was de-fined as serum creatinine greater than 2.5 mg/dl formore than 7 days or requiring dialysis [11]. Stroke wasdefined as a new focal or global dysfunction of cerebralfunction lasting over 24 h. Gastro-intestinal complica-tions included gastrointestinal bleeding, intestinal ob-struction and other serious gastrointestinal dysfunction.Incision infection meant the chest or leg wound infec-tion requiring antibiotic therapy or operation [12].MSOF (a severe dysfunction of at least two organ sys-tems lasting for more than 24 h, as stated by the

Ji et al. Journal of Cardiothoracic Surgery (2015) 10:16 Page 3 of 7

Consensus Conference of the American College of ChestPhysicians and the Society of Critical Care Medicine[13]) was recorded. In addition, duration of mechanicalventilation and length of intensive care unit (ICU) staywere also recorded.

Statistics analysisStatistical analysis was performed using the SPSS 17.0statistical software package. All p values <0.05 were con-sidered to be statistically significant. Normal distributionof measurement data was shown by mean ± standard de-viation, and was compared between the groups by t-test.Fisher’s exact test was employed to compare enumer-ation data. In order to further confirm the reliability ofresults, mortality and major postoperative morbiditieswere further analyzed by multiple logistic regressionanalysis. The covariate of regression analysis included age,gender, body mass index, previous disease history (in-cluded diabetes, hyperlipaemia, hypertension, chronicobstructive pulmonary disease, myocardial infarction,and peripheral vascular disease), left ventricular ejec-tion fraction, application of the internal mammaryartery, use of cardiopulmonary bypass, and number ofgrafts.

ResultsStudy populationFrom January 2007 to December 2013, after obtainingapproval by the ethic committee, a total of 3856 con-secutive patients undergoing isolated CABG were en-tered into this study. One hundred and twenty-sixpatients were excluded due to incomplete informationfrom preoperative smoking records, and finally 3730 pa-tients (3207 male patients and mean 63.6 ± 9.5 years)were retrospectively analyzed. According to preoperativesmoking records, 2186 patients (accounting for 58.6%)who had more than 1 cigarette every day with continu-ing at least 1 year were included into a smoking group,and the other 1544 patients without a history of smokinginto a non-smoking group. And then, the smoking groupwas divided either into a former smoking subgroup(smokers with smoking cessation over 1 month beforeCABG surgery, n = 614) or a current smoking group(persistent smokers, n = 1572).Baseline data of all included patients are shown in

Table 1. Comparing with the non-smoking group, thesmoking group was more likely to present with male(98.6% vs. 68.1%, p < 0.0001), history of myocardial in-farction (53.0% vs. 46.7%, p < 0.0001), chronic obstruct-ive pulmonary disease (COPD) (14.0% vs. 6.1%, p <0.0001), and high body mass index (BMI) (25.1 ± 3.1 kg/m2 vs. 24.8 ± 3.2 kg/m2, p = 0.0041), but was less likelyto hypertension (50.5% vs. 58.1%, p < 0.0001) and hyper-lipidemia (31.3% vs. 38.7%, p < 0.0001). Patients in the

smoking group was younger (62.2 ± 9.4 years vs. 65.7 ±9.7 years, p < 0.0001) and had lower left ventricular ejec-tion fraction (LVEF) (57.9 ± 9.9% vs. 59.7 ± 9.0%, p <0.0001) as compared to the non-smoking group. Andcomparing with the non-smoking group, the formersmoking subgroup was more likely to present with male(98.0% vs. 68.1%, p < 0.0001), history of myocardial in-farction (51.9% vs. 46.7%, p = 0.0029), COPD (15.8% vs.6.1%, p < 0.0001), and high BMI (25.2 ± 3.0 kg/m2 vs.24.8 ± 3.2 kg/m2, p = 0.0017), but was younger (60.7 ±8.8 years vs. 65.7 ± 9.7 years, p < 0.0001) and hadlower LVEF (57.5 ± 9.7% vs. 59.7 ± 9.0%, p < 0.0001). Inaddition, the current smoking subgroup was more likelyto present with male (98.9% vs. 68.1%, p < 0.0001), his-tory of myocardial infarction (53.4% vs. 46.7%, p =0.0002) and COPD (13.3% vs. 6.1%, p < 0.0001), but wasless likely to hypertension (48.3% vs. 58.1%, p < 0.0001)and hyperlipidemia (30.0% vs. 38.7%, p < 0.0001) as com-pared to the non-smoking group. Comparing with thenon-smoking group, the current smoking subgroup wasless likely to undergoing CABG with cardiopulmonarybypass (17.6% vs. 27.1%, p < 0.0001) and had lower LVEF(58.1 ± 9.8% vs. 59.7 ± 9.0%, p < 0.0001).

Early outcomes following CABGThe comparison of surgical mortality and major postop-erative morbidities between the smoking group andnon-smoking group is shown in Table 2. A total of 92patients were died, with a surgical mortality of 2.5%. Thesmoking group had a low surgical mortality as comparedto the non-smoking group, but no statistical differencewas found (2.2% vs. 2.8%, p = 0.3348). The smokinggroup had significantly higher incidence of postoperativepulmonary complications (7.1% vs. 4.5%, p = 0.0010),and significantly longer duration of mechanical ventila-tion (9.8 ± 2.6 h vs. 9.4 ± 2.4 h, p < 0.0001) as comparedto the non-smoking group. There were no statisticallysignificant differences between the smoking group andthe non-smoking group in postoperative myocardial in-farction, low cardiac output syndrome, new onset atrialfibrillation, cardiac arrest or ventricular fibrillation, acutekidney injury, stroke, gastro-intestinal complications, in-cision infection, and multiple system organ failure.The comparison of surgical mortality and major post-

operative morbidities between the current smoking sub-group and non-smoking group is shown in Table 2.There was no significant difference in surgical mortalitybetween the 2 groups (2.0% vs. 2.8%, p = 0.1579). Com-paring with the non-smoking group, the current smok-ing subgroup had significantly higher incidence ofpostoperative pulmonary complications (7.8% vs. 4.5%,p = 0.0002) and significantly longer duration of mechanicalventilation (p < 0.001). There were no statistically signifi-cant differences between the two groups in postoperative

Table 1 Baseline data of all included patients

Variables Non-smokinggroup

Smoking group

Total Former smoking subgroup Current smoking subgroup

(n = 1544) (n = 2186) (n = 614) (n = 1572)

Age (years) 65.7 ± 9.7 62.2 ± 9.4* 60.7 ± 8.8* 65.3 ± 9.2

Male 1051 (68.1%) 2156 (98.6%)* 602 (98.0%)* 1554 (98.9%)*

BMI (kg/m2) 24.8 ± 3.2 25.1 ± 3.1* 25.2 ± 3.0* 24.9 ± 3.1

Familial history of CAD 1425(92.3%) 1994(91.2%) 556(90.6%) 1438(91.5%)

Diabetes mellitus 559(36.2%) 783(35.8%) 230(37.5%) 553(35.2%)

Hypertension 897(58.1%) 1103 (50.5%)* 344(56.0%) 759 (48.3%)*

Hyperlipemia 597(38.7%) 684 (31.3%)* 212(34.5%) 472 (30.0%)*

COPD 94 (6.1%) 306 (14.0%)* 97 (15.8%)* 209 (13.3%)*

History of MI 721(46.7%) 1158 (53.0%)* 319 (51.9%)* 839(53.4%)*

Prior CVA 240(15.5%) 348(15.9%) 108(17.6%) 240(15.3%)

Coronary artery lesion

Double-vessel 134(8.7%) 198 (9.0%) 54 (8.8%) 144(9.1%)

Triple-vessel 1408(91.2%) 1985(90.8%) 558(90.9%) 1427(90.8%)

Left main 378(24.5%) 529 (24.2%) 147 (23.9%) 382 (24.3%)

SYNTAX score

Low: ≤ 22 278 (18.0%) 306 (14.0%) 101 (16.4%) 200 (13.1%)

Intermediate: 23-32 793 (51.4%) 1194 (54.6%) 324 (52.8%) 870 (55.3%)

High: ≥33 473 (30.6%) 686 (31.4%) 189 (30.8%) 497 (31.6%)

LVEF (%) 59.7 ± 9.0 57.9 ± 9.9* 57.5 ± 9.7* 58.1 ± 9.8*

>50% 1275 (82.6%) 1631 (74.6%)* 463 (75.4%)* 1168 (74.3%)*

35-50% 178 (11.5%) 407(18.6%)* 99 (16.1%)* 308 (19.6%)*

<35% 91 (5.9%) 148 (6.8%)* 52(8.5%)* 96 (6.1%)

Emergence operation 123 (8.0%) 179 (8.2%) 49 (7.9%) 130 (8.3%)

On-pump CABG 418(27.1%) 439 (20.1%)* 163(26.5%) 276 (17.6%)*

CPB (min) 78.2 ± 31.4 79.6 ± 27.8 75.5 ± 24.8 80.1 ± 28.4

ACC (min) 57.2 ± 20.6 58.5 ± 19.5 57.4 ± 18.6 59.4 ± 20.6

Use of IMA 1518 (98.3%) 2144 (98.1%) 603 (98.2%) 1541 (98.0%)

Number of grafts 3.3 ± 0.5 3.3 ± 0.4 3.3 ± 0.6 3.3 ± 0.4

Fisher’s exact test was employed to compare enumeration data, and t-test to compare measurement data.*p < 0.05 (as compared to Non-smoking group).BMI, body mass index; CAD, coronary artery disease; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; CVA, cerebro-vascular accident; LVEF,Left ventricular ejection fraction; CABG, coronary artery bypass grafting; On-pump CABG, CABG with cardiopulmonary bypass; CPB, cardiopulmonary bypass; ACC,aortic cross clamp; IMA, internal mammary artery.

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myocardial infarction, low cardiac output syndrome, newonset atrial fibrillation, cardiac arrest or ventricular fibril-lation, acute kidney injury, stroke, gastro-intestinal com-plications, incision infection, and multiple system organfailure.The comparison of early outcomes following CABG

between the former smoking subgroup and the non-smoking group is shown in Table 2. There wereno statistically significant differences between the 2groups in surgical mortality, major postoperativemorbidities, and length of mechanical ventilation andICU stay.

Logistic regression analysisThe impact of smoking on surgical mortality and majorpostoperative morbidities after adjustment for potentialconfounders (age, gender, BMI, diabetes, hyperlipaemia,hypertension, COPD, recent myocardial infarction, per-ipheral vascular disease, LVEF, application of internalmammary artery, use of cardiopulmonary bypass, num-ber of grafts) is shown in Table 3. In multivariate logisticregression analysis, smoking had an independent influ-ence on the development of postoperative pulmonarycomplications (OR = 1.92, 95% CI 1.08-3.64). And, multi-variate logistic regression analysis also showed that the

Table 2 Early clinical outcomes after CABG surgery

Non-smokinggroup (n = 1544)

Smoking group

Total Former smoking subgroup Current smoking subgroup

(n = 2186) (n = 614) (n = 1572)

Surgical mortality 43(2.8%) 49(2.2%) 18(2.9%) 31(2.0%)

MI 16(1.7%) 24(1.1%) 8(1.3%) 16(1.0%)

LCOS 282(18.3%) 433(19.8%) 124(20.2%) 309(19.7%)

New onset AF 177(11.5%) 227(10.4%) 78(12.7%) 95(9.5%)

Ventricular fibrillation 29(1.9%) 46(2.1%) 15(2.4%) 31(2.0%)

Pulmonary complications 70 (4.5%) 156 (7.1%)* 34 (5.5%) 122 (7.8%)*

Mean ventilation time (h) 9.4 ± 2.4 9.8 ± 2.6* 9.5 ± 2.3 9.9 ± 2.7*

Renal failure 38(2.5%) 53(2.4%) 14(2.3%) 39(2.5%)

Stroke 31(2.0%) 20(0.9%) 5(0.8%) 15(1.0%)

GI complications 82(5.3 %) 120(5.5%) 19(3.1%) 101(6.4%)

Incision infection 21(1.4%) 33(1.5%) 9(1.5%) 24(1.5%)

MSOF 25(1.6%) 29(1.3%) 6(1.0%) 23(1.5%)

Mean length of ICU stay (h) 33.5 ± 6.9 34.2 ± 6.8 33.5 ± 6.1 34.5 ± 7.0

Mean was compared between the groups by t-test, and enumeration data by Fisher’s exact test.*p < 0.05 (as compared to Non-smoking group).MI, myocardial infarction; LCOS, low cardiac output syndrome; AF, atrial fibrillation; GI complications, gastro-intestinal complications; MSOF, multiple system organfailure; ICU, intensive care unit.

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risk of postoperative pulmonary complications in persist-ent smokers was 2.41 times than that in non-smokers,whereas the risk of postoperative pulmonary complica-tions in smokers with smoking cessation over 1 monthbefore CABG was similar to non-smokers.

DiscussionAlthough the public gradually raised awareness of thedangers of smoking and Chinese government attachedgreat importance to the tobacco control, the prevalencerate of smoking in China remains unacceptably high in

Table 3 Logistic regression analysis

Events Non-smokinggroup

Smoking group

Total

OR (95% CI)

Surgical mortality 1.0 1.10 (0.42-2.73)

MI 1.0 1.23 (0.48-3.12)

LCOS 1.0 1.13 (0.82-1.51)

New onset AF 1.0 1.07 (0.74-1.61)

Ventricular fibrillation 1.0 1.43 (0.65-3.14)

Pulmonary complications 1.0 1.92 (1.08-3.64)*

Renal failure 1.0 1.20 (0.54-2.63)

Stroke 1.0 0.92 (0.41-2.14)

GI complications 1.0 1.55 (0.45-4.75)

Incision infection 1.0 1.31 (0.44-4.78)

MSOF 1.0 1.14 (0.44-3.10)

*p < 0.05 (as compared to Non-smoking group).

the current era [4]. The prevalence rate of smoking inpatients with coronary artery disease undergoing isolatedCABG surgery in this study touched 58.6%, with farabove 30% in the Western countries reports [14-16],suggesting that the task of tobacco control was difficult,and moreover, time was pressing. There were rare re-ports about the impact of smoking on clinical outcomesin Chinese patients undergoing isolated CABG. Basedon these, this study aimed to evaluate the impact of per-sistent smoking vs. smoking cessation over 1 month be-fore surgery on early postoperative clinical outcomes by

Former smoking subgroup Current smoking subgroup

OR (95% CI) OR (95% CI)

0.85 (0.31-2.42) 1.41 (0.42-3.91)

1.12 (0.43-2.89) 1.45 (0.63-3.49)

1.22 (0.82-1.84) 1.05 (0.85-1.38)

0.95 (0.62-1.62) 1.41 (0.77-2.21)

1.93 (0.78-4.82) 1.31 (0.58-2.95)

1.32 (0.61-3.16) 2.41 (1.21-4.64)*

1.05 (0.41-2.97) 1.38 (0.52-3.10)

0.41 (0.11-1.83) 0.29 (0.08-1.31)

0.51 (0.11-3.76) 1.79 (0.55-5.48)

2.11 (0.55-8.93) 1.17 (0.29-5.14)

0.62 (0.21-2.99) 1.51 (0.48-4.03)

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reviewing 3730 Chinese patients with or without a his-tory of smoking undergoing isolated CABG surgery.The major finding of this study was that comparing

with non-smokers, persistent smokers were more likelyto suffer from postoperative pulmonary complications,whereas smokers with smoking cessation over 1 monthbefore CABG surgery did not increase the incidence ofpostoperative pulmonary complications. In this study,univariate analyses showed that persistent smokers had ahigher incidence of postoperative pulmonary complica-tions (7.8% vs. 4.5%, p = 0.0002) as compared to non-smokers, whereas smokers with smoking cessation over1 month before CABG surgery and non-smokers shareda similar incidence of postoperative pulmonary compli-cations (5.5% vs. 4.5%, p = 0.3183). Furthermore, mul-tiple logistic regression analysis showed that the risk ofpostoperative pulmonary complications in persistentsmokers was 2.41 times than that in non-smokers,whereas the risk of postoperative pulmonary complica-tions in those smokers with smoking cessation over1 month before CABG was similar to non-smokers.Reason of this difference may be that smoking causedobstructive ventilation function disturbance and aggra-vated respiratory disease, contributing to postoperativepulmonary complications, whereas smoking cessationover 1 month may gradually improve ciliary functionand macrophage phagocytic function, and steadily de-creased the sputum, resulting in the reduction of post-operative pulmonary complications in a few weeks[17,18]. This result was consistent with previous stud-ies [2,3,14,15,17,18]. In addition, smokers with smok-ing cessation over 1 month before CABG surgery andnon-smokers shared a similar incidence of major post-operative morbidities, suggesting that smoking cessationmore than 1 month before CABG surgery was expected toreduce early major morbidities after CABG surgery and toaccelerate recovery.This study showed smokers were less likely to hyper-

tension and hyperlipidemia as compared to non-smokers.Reason of this difference may be the age, regarding thatsmokers suffered with coronary atherosclerosis receivedtreatment in their youth, and thus were less likely to suf-fering from senile diseases, such as hypertension, hyper-lipidemia [19]. In this study, smokers were more likely tohistory of myocardial infarction and had lower left ven-tricular ejection fraction as compared to non-smokers.Higher incidence of myocardial infarction, in associationwith reduction of cardiac function, may lead to more ser-ious condition, hence may unfavourable for postoperativerecovery. This study also showed that there was no signifi-cant difference in surgical mortality between smokers andnon-smokers, which was consistent with Al-Sarraf N’sstudy [20]. Smokers were younger and had lower inci-dence of hypertension and hyperlipidemia, but had higher

incidence of chronic disease obstructive pulmonary dis-ease and history of myocardial infarction with poor cardio-pulmonary function, and then had the similar surgicalmortality to non-smokers [3,14].So far, few studies have assessed the relationship be-

tween persistent smoking vs. smoking cessation beforesurgery and early clinical outcomes of Chinese patientsundergoing isolated CABG surgery. This study showedthat persistent smoking increased postoperative pulmon-ary complications, which not only prolonged rehabilita-tion, but also may cause other morbidities, consequentlyincreasing the financial burden. Smoking cessation over1 month before CABG surgery was expected to reduceearly major morbidities after CABG surgery.There are some limitations of this study. This study

was only a retrospective observational trial, which mayinfluence the generalizability. Secondly, relatively lowpostoperative morbidities and mortality in this studymay cause false negative result, which remained to be re-solved by expanding the sample size. Finally, this studyfocused on the early clinical outcomes, and furtherfollow-up study involving larger sample size were neededto determine the effect of smoking on long-term clinicaloutcomes after CABG surgery.

ConclusionsPersistent smokers had a higher incidence of pulmonarycomplications following CABG as compared to non-smokers. Smoking cessation more than 1 month beforeCABG surgery was expected to reduce early majormorbidities after CABG surgery.

AbbreviationsCABG: Coronary artery bypass grafting; LCOS: Low cardiac output syndrome;MSOF: Multiple system organ failure; ICU: Intensive care unit; COPD: Chronicobstructive pulmonary disease; BMI: Body mass index; LVEF: Left ventricularejection fraction; OR: Odds ratio.

Competing interestsThe authors declare that they have no competing interests.

Authors’ contributionsYQM and WJD made contributions to conception, design and coordinationin this study and revised it critically for important intellectual content. QJ andHZ participated in the design of the study and drafted the manuscript. YQSand RHM carried out the data collection and statistical analysis. All authorsread and approved the final manuscript.

Authors’ informationQiang Ji and Hang Zhao is the co-first author.

Author details1Department of Thoracic Cardiovascular Surgery of Tongji Hospital of TongjiUniversity, 389 Xincun Rd, Shanghai 200065, P.R. China. 2Master student,Tongji University, 1239 Siping Rd, Shanghai 200092, P.R. China. 3Departmentof Cardiovascular Surgery of Zhongshan Hospital of Fudan University, 180Fenglin Rd, Shanghai 200032, P.R. China.

Received: 21 September 2014 Accepted: 18 January 2015

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